Power loss and stumbling at high rpms - Saab 900 Bulletin Board - Saabnet.com
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The 1993 900 Turbo employs the three separate systems to complete engine management which includes the BOSCH LH 2.4 fuel management, a SAAB APC for turbocharger boost control, and an ignition system.
The BOSCH LH 2.4 fuel management was designed as a very adaptive system, but may be more temperamental relative to any pressure loss when under full turbocharger/APC boost pressure, and you will want to insure that the entire system is checked for any potential escape route to pressures which may confuse the air mass metered intake causing symptoms as you described. Many shops will check the turbocharger to rubber intercooler boots for cracks as this is very common as well as all vacuum lines at the intake manifold which should be sealed when pressurized.
The ignition systems in this era 900 employs an ignition cut which may defeat spark when any misfire is detected. This could easily be caused by installation of an incorrect spark plug or incorrect plug gap. Make certain that only NGK spark plugs are in use, and BCP-6ES or BCP-7EV gapped at .026”.
The APC boost control systems may not allow for maximum charging pressures if any non shielded spark plug wire are in service, and you will want to insure that only OEM SAAB wire sets(BOUGICORD) are in use. In many cases, there could be an improved maximum APC charging pressure when any aftermarket ignition wires are replaced with a shielded wire set. This era 900 also employs an over-boost protection which is an air mass related fuel pump defeat typically at 1 bar of pressure or 1/2 red on the dash board APC gauge.
Thanks again for posting at TSN, and we are open Saturdays until 6PM if there should be any questions!
Gary K. at SWEDISH DYNAMICS, INC.
->Posting last edited on Sat, 17 Aug 2019 20:53:30.
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